Cleavage of the Nitrous Oxide NN Bond by a Tris(amido)molybdenum(III) Complex

Abstract

Of great si&icance in both biological and synthetic systems are two-electron processes in which a divalent atom such as oxygen is completely transferred between two reaction partners.' Until now, the endogenous three-electron atom transfer process has been limited to examples of intermetallic nitrogen atom transfer as exemplified by the reaction (TTP)Cr + N=Mn(TTP) -(TTP)CFN 4-Mn(TTP).2 In the present work we establish a three-electron redox process in which a nitrogen atom from nitrous oxide is transferred to a molybdenum(II1) coordination complex.The complex Mo(NRAr)3 (1; R = C(CD3)2CH3, Ar = 33-C6H3Me2) was prepared for this work since d3 1 could conceivably engage in three-electron redox processes. Of the various possibilities, N-atom transfer was a particularly attractive target since stable nitrido complexes of the kind N=MoX3 (X = alkyl,3 amide? or &oxide5) are known. In a typical preparation, M o C~~( T H F )~~ (4.164 "01) and Li(NRAr)(OEt2)7 (8.315 m o l ) were added to 70 mL of cold (-100 "C) ether, and the mixture was stirred for 2.5 h after warming to 28 "C. The precipitated LiCl and excess MoC13(THF)3 were removed by filtration. Analysis of the filtrate by 2H NMR spectroscopy showed only one major product, with a relatively sharp (Avll2 = 35 Hz) signal at 64.6 ppm corresponding to the 2H-labeled tert-butyl groups in paramagnetic M O ( N R A~)~.~ The filtrate was concentrated and cooled to -35 "C under an argon atmosphere to produce orange-red, crystalline Mo(NRAr)3 (mp 126-128 "C, yield 70%)? MO(NR&)3 (1) is extremely oxygen-and (1) Holm, R. H.; Donahue,

Alkyne Metathesis: Catalysts and Synthetic Applications

“…Following on the pioneering work of Cummins on the molybdenum species of the general type Mo[NA C H T U N G T R E N N U N G (tBu)Ar] 3 24 (the analogue of compound 17), [34][35][36][37] which activate the triple bond of dinitrogen in a stoichiometric fashion, Fürstner and co-workers investigated the reactivity of this type of compounds for alkyne metathesis. Although compound 24 (Ar = 3,5-dimethylbenzene) was not metathesis active on its own, treatment of 24 in toluene with > 2 equivs.…”

Total Synthesis of Myxovirescin A1

“…A standard extractive work up followed by flash chromatography (hexanes/EtOAc 4:1) afforded product 15 (117 mg, 90 %) as a colorless oil. 1 A C H T U N G T R E N N U N G (17Z)-18-Methoxymethyl-oxa-cyclooctacos-17-en-15-yne-2,10-dione (16): Complex 20 (7.5 mg, 0.016 mmol) [20] , [59] and CH 2 Cl 2 (120 mL, 1.87 mmol) were successively added to a solution of diyne 15 (60 mg, 0.12 mmol) in toluene (85 mL) and the resulting mixture was stirred at 80 8C for 15 h. For work up, the reaction was quenched with MeOH (5 mL), all volatile materials were evaporated and the residue was purified by flash chromatography (hexanes/ (6).…”

A Comparison of N2 Cleavage in Schrock's Mo[N3N] and Laplaza–Cummins' Mo[N(R)Ar]3 Systems

“…[11,12,13,14] The N 3 N ligand binds to metals in a tetradentate manner, creating a ligand cage with an amine cap, [10] as shown in Figure 1. With the exception of the cap, the N 3 N ligand system is similar to Laplaza and Cummins M[N(R)Ar] 3 (R = tBu, Ar = 3,5-C 6 H 3 Me 2 ) system, [15][16][17] in that it has three amide donors arranged in a trigonal plane around the metal centre, a similar orientation of the R groups, and the same overall charge on the metal complex. R = 3,5-(2,4,6-iPr 3 C 6 H 2 ) 2 C 6 H 3 (HIPT), which is capable of converting N 2 to ammonia catalytically, reacts with N 2 in a similar manner to Mo[N(R)Ar] 3 (R = tBu, Ar = 3,5-C 6 H 3 Me 2 ) to form a dinitrogen-bridged dimer intermediate, but unlike its three-coordinate counterpart, N 2 cleavage is not observed.…”